Porcelain firing curve

I haven`t manage to find good porcelain firing curve. I always have big problems with warping. Now I decided to figure this out ... there are three bodies (all "low fire" porcelain, cone from 9-10) in my studio which I would like to try.
I will fire to cone 9 / 10, actually 1240 celsius (I don`t quite understand those cones, there are 6 different temperatures for cone 9). All bodies should be fired above 1220.

Because there is no grog in porcelain it always will slump, warp and move at high firing temps. It needs to be supported once the shape moves out from being a straight self supporting cylinder. There are many options for supporting it during firing. Another research week ahead!
Controlled cooling also helps eliminate cracks and warping.

Chris Campbell

Contemporary Fine Colored Porcelain
www.ccpottery.com

TRY ... FAIL ... LEARN ... REPEAT

" ... If a sufficient number of people are different, no one has to be normal"
Fredrick Bachman

Our studio manager can fire her kiln almost 7 days a week - another prominent ceramicist in our city referred to her kiln as a microwave. She works with porcelain, fires to 1260C She gets occational warping, but not a lot. and she works extremely thin.

I use spann rings for my work. I dry my cups and bowls upside down on them, and it helps to prevent my work to warp in the drying process.

If your claybody is uneven in thickness, it can pull egg shapes in the glaze fire. If you slipcast, make sure that your slip is not too thick and sluggish when it pours out - this will cause the area that the slip is running off, to be slightly thicker. I know that one is 'not allowed to' but I actually shake my molds when I decant my slip.

I haven`t manage to find good porcelain firing curve. I always have big problems with warping. Now I decided to figure this out ... there are three bodies (all "low fire" porcelain, cone from 9-10) in my studio which I would like to try. I will fire to cone 9 / 10, actually 1240 celsius (I don`t quite understand those cones, there are 6 different temperatures for cone 9). All bodies should be fired above 1220.

I am making test pieces- casting from 2-4 mm.

Another question - has anybody tried raw glazing with porcelain?

Any suggestions?Where is the crucial point for warping?

Thank you a lot!

Raw glazing porcelain is in some ways easier then stoneware clays; they often shrink less during drying and more in the fire than stoneware. I would recommend dipping during leather hard stag or slightly dryer. If the pot collapse after dipping try adding more water to the glaze mix and try to shake of excess glaze when glazing.The glaze needs to shrink more then usual to fit well so the glaze recipe should be high on plastic clay (kaolin can be rather unplastic). Adding up to 5% bentonite adds alot of plasticity but many glazes work as is if used at the right dryness of the pot..If you are unexperienced with raw glazing expect a bit of testing before you get it just right. Good luck!

hi Inya, yea that is my spann rings (and black clay work drying on it. I have rings in various diameters, with a gentle curve. If you want to make them, it is better to have a master made of rubber - otherwise it could be tricky to get the spann ring out :-) And I have close to a 100 if not more in the studio.

I have never found porcelain to need a firing schedule that is any different than stoneware. I have fired on several different schedules here at my shop with no difference whatsoever. Glazes, on the other hand, will be greatly affected by the firing schedule.

I think the main issues with warping ire the formula of the body itself and the construction of the ware. Some porcelains warp more than others. It just depends on the formula. Generally, the glassier the body the more likely it is to warp. Uneven pots will warp more. Big pots tend to slump more.

Inya, I am sorry - i spoke to her, she told me that it is on the firing schedule charts at every kiln at the studio, and I forgot to look. I will do that tomorrow morning first thing (at least we are a the same time day & night) and post from work.

Inya, I am sorry - i spoke to her, she told me that it is on the firing schedule charts at every kiln at the studio, and I forgot to look. I will do that tomorrow morning first thing (at least we are a the same time day & night) and post from work.

hi, I fire my porcelain straight up to 1300 as it flattens out my pieces. I use paper clay sheets to cut my tiles and I have started placing the "off cuts" of the paper clay sheet around the edges of my porcelain tiles to flatten them while drying and it works very well. I don't have any experience of firing porcelain pots....sorry.